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Thread: Chronograph Challenge and chasing ES/SD

  1. #41
    Boolit Grand Master
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    Larry, I very much appreciate the information you have shared, the details/opinions you give....and your honesty.

    I have learned more from this thread than expected. It has cause me to question my methods...methods that seemed to have worked for the 50+ years I have been putting holes in paper. I am reminded of the phrase, "You don't know what you don't know".

    I have a new Howa .223 bolt gun I am loading for, and a new hunting bullet for one of the .308's I am wringing out. I have already made incremental loads for the .223 using 5 rounds per charge. Your opinion regarding at least 10 rounds to determine ES and SD makes sense. Even with my method of 5 shot groups I fire 5 groups to "prove" a load as there is too much variation to depend on one "wallet" group to tell the story.

    With the requirements I have, varmints to 300 yards and deer to 400 yards, it may not matter much, but I have decided to at least try a more rigorous method as you have suggested. "Wasting" components and trigger time is never a 'waste' anyway...LOL.

    I will still award the chronograph (maybe lightly used) or its equivalent value if I decide to keep it.

    Again, thank you everyone for contributing.
    Don Verna


  2. #42
    Boolit Buddy 414gates's Avatar
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    Quote Originally Posted by Kosh75287 View Post
    When I get a certain velocity for a given charge weight then get a roughly proportional increase in velocity for an increase in powder charge, it SUGGESTS that I'm still in the "safe zone" of the work-up. If I go up on charge weight and get a very small increase, NO increase, or even a DECREASE in velocity, that suggests to me that further charge increases are likely to unsafe, and I should back off.
    This is what nearly everybody says they do.

    It makes no sense to me that no increase in velocity corresponds to a higher powder charge. Powder is gas. More powder more gas.

    I have tried testing for that, but never been able to prove it to myself systematically and predictably.

    Which is why I measure for pressure. It is never wrong.

  3. #43
    Boolit Bub
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    I have been shooting over chronographs since they became affordable. I now have four including a 35P and a LabRadar. I never develop a load by chronograph but by pressure. It's an interesting offer but I don't need any more. Best, Squid Boy

  4. #44
    Boolit Master
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    The point of more powder and less speed is valid in some cases. I have found that as a powder charge is compressed, velocity may slow down until enough powder is added to make up for the reduced powder ignition due to powder compression. I ran into this in several rifles, .243, .308, and even the .45-70. It always occurred when a powder charge went from 98-99% case fill to moderately compressed, velocity could be regained by going to 'hotter' magnum primer OR adding yet another grain or two of powder, but there was a spot where another grain or two slowed things down, my best guess is the compression reduced ignition and or modified burn rate.

  5. #45
    Boolit Master
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    I have used chronogaph extensively while building loads for long rainge work. 800,9000,1000,+. Every time powder lot changes, load changes, i spent over 5 years working on a 45/70 to get it to shoot the way i wanted, out to over 1000yds. Thats with soft lead, 500gr + bullet, iron sights, blackhorn powder, make my own lube, could not find any lube, that did what i wanted. Many who thought they knew, said coudn't be done. Rifle and load will hold the 10 ring at 1000yds. No problem, if i do my part. Same load work up for .308,30.06,6br,300mag,6x22-250 or any of the rest. This will work for close ranges, to help eliminate varibles. Only intresting gun out there, is a super accurate one.

  6. #46
    Boolit Master
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    How do you measure for pressure ???

  7. #47
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    Quote Originally Posted by BLAHUT View Post
    How do you measure for pressure ???
    I use an Oehler M43 PBL and also a Pressure Trace II system.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  8. #48
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    Quote Originally Posted by BLAHUT View Post
    How do you measure for pressure ???
    I use an Oehler M43 PBL and also a Pressure Trace II system. Both require the use of a computer for the software program. I use a separate laptop for each and by affixing 2 strain gauges 180 degrees apart I can simultaneously measure the psi of a single shot with each device.

    The M43 PBL also is a chronograph which includes muzzle and target screens which records screened velocity at 15' from muzzle then converts to muzzle velocity. The target screens (out t0 100 yards) measure the remaining velocity/TOF and the convert to BC for each shot.

    The Pressure Trace II measures only the time pressure curve (trace) and associated data with it. A separate chronograph is required for velocity measurement.

    Both require a strain gauge be affixed to the barrel of the test firearm directly over the center of the chamber. I affix the strain gauges at the SAAMI specified location for Piezo transducers. Thus, with some shorter cartridges I use a single shot (mostly a Contender) so the gauge can be affixed directly over the chamber at the specified SAAMI location for Piezo transducers.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  9. #49
    Boolit Buddy 414gates's Avatar
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    Quote Originally Posted by MostlyLeverGuns View Post
    The point of more powder and less speed is valid in some cases. I have found that as a powder charge is compressed, velocity may slow down until enough powder is added to make up for the reduced powder ignition due to powder compression. I ran into this in several rifles, .243, .308, and even the .45-70. It always occurred when a powder charge went from 98-99% case fill to moderately compressed, velocity could be regained by going to 'hotter' magnum primer OR adding yet another grain or two of powder, but there was a spot where another grain or two slowed things down, my best guess is the compression reduced ignition and or modified burn rate.
    Good info, thank you.

    I never came across this in my testing of max loads in 375 RUM, but I got around having to compress the powder by using a long powder drop.

  10. #50
    Boolit Buddy
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    Quote Originally Posted by Larry Gibson View Post
    An interesting observation I've made is the group distribution of shots vs the SD/ES ratio. This observation is not a 100% given but falls into the most often observed category. The more groups (10 shot) of a given load that is fired the more likely the shot dispersion I'll mention will be observed.
    An interesting observation indeed Larry, and one begging for explanation.

    I'm no statistician, though I did a unit at University and spent my career working with scientific types. That said, a real statistician will find my depth in a single sentence.

    Our interest no doubt is in how well samples (groups) represent the whole population. For the most part we assume that the distribution of observations (e.g. velocities) in a population is "normal". Effectively, that means half the observations are above the mean, generally referred to as "average" (total of all observations divided by number of observations), and half below, and all of it following a bell shaped curve. If it is otherwise, then the distribution is "skewed", and may be better described by the "median" - the value that falls half way along the distribution. Examples are rainfall, and the weights of cast bullets before culling. In both examples the median tends to be less than the mean. The median downplays extreme values. In a "normal" distribution, mean and median will be the same.

    My recollection of statistical basics is that we expect 95% of observations to fall within 1.96 SDs of the mean, so for mugs like me, SD of the POPULATION should be about 25% of the ES. Back at the sample level (groups), this is unlikely to be the exact case due to small sample size. Translating velocity variations to group pattern and size is another step that I'll leave alone.

    When SD is not 25% of ES can we get different SDs out of a string of numbers with the same ES and mean? Answer is yes. A hollow distribution, i.e. a group of high numbers and a group of low numbers all on the edge of the ES, will produce a higher SD than another group with a bunch in the middle with just one number defining each end of the ES.

    This deviation from 25% for SD/ES should become less as sample size increases but your observation Larry, that it becomes clearer as number of groups increases, suggests that aberrant SD/ES is not just a sample size thing and that it could be telling us something bigger.

    The answer could be that the distribution for our load is NOT normal, and that the apparent misalignment of SD and ES are telling us something diagnostic about the distribution itself.

    I'd love to see a response from a proper statistician or mathematician.
    Last edited by Wilderness; 06-26-2022 at 07:53 PM.
    It'll be handy if I never need it.

    Insomniac, agnostic, dyslectic - awake all night wondering if there is a Dog.

  11. #51
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    Wilderness

    "This deviation from 25% for SD/ES should become less as sample size increases but your observation Larry, that it becomes clearer as number of groups increases, suggests that aberrant SD/ES is not just a sample size thing and that it could be telling us something bigger.

    The answer could be that the distribution for our load is NOT normal, and that the apparent misalignment of SD and ES are telling us something diagnostic about the distribution itself.
    "

    Probable best summation of my observations.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  12. #52
    Boolit Grand Master
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    Wilderness, plotting the data will tell us if a distribution is normal. That is shown by looking at the weight of cast bullets where there is a "hard stop" on maximum weight. (ie you cannot put 10 lbs of manure in a 5 lb bag). Cast bullets cannot weigh more than the maximum fill of a mold, but can weigh less due to a variety of factors (cadence, inclusions, melt temperature changes during casting, inconsistency of alloy during a session as ingots are added if alloy varies).

    The type of distribution should be apparent with velocity data. If someone wants to send me a string of 20 or so velocity readings for the same load in the same gun fired on the same day I can plot them. What cannot be determined is if a normal distribution is what every load and gun will produce but it would be a start. It would be interesting to see the distribution with a SD/ES of 25% with one load and 15% with another, and another with 40%

    I have some stuff to address today and will determine the winner of the challenge. I have learned a lot from this thread. My current "gut feel" wrt to the challenge is unchanged. For varmint loads for a .223 to 300 yards, and .308 deer loads to 400 yards, SD and ES may not matter much if the loads group well at 100 and 200 yards. But this thread has triggered some testing I want to do. That will be educational (for me), and I will share the results when I am done.

    BTW, I see the value of a chronograph for other needs, and I acknowledged that in my first post. My query related to using a chronograph as a tool for developing loads for more "normal" needs.
    Don Verna


  13. #53
    Boolit Master
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    I use a Labradar chronograph to explore powder applicability in pistol-caliber carbines. Longer barrels really do prefer slower powders for increased velocity. I would have guessed that, the chrono demonstrated it. Same in short-barreled revolvers.
    Loren

  14. #54
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    I use my chronograph now, mainly to maintain the same fps from lot to lot in SAME powder BRAND> for load consistency, carterage to carterage, With soft lead to keep load consistent and cut vertical displacement on target, ALSO ON ALL MY OTHER COMPITISION LOADS WITH JACKED BULLETS, I WEIGH EACH BULLET AND POWDER, more critical with the increase in distance. I WEIGH EVER POWER CHARGE, ELECTRONIC SCALE, EVERY BULLET IN A 50 ROUND BOX WILL WEIGH THE SAME, BEFORE LUBE, EVERY CARTERAGE IN BOX WILL WEIGH WITH IN 1 GR. OF THE NEXT, FOR THE ENTIRE BOX, SAME FOR JACKED BULLETS, ALL BULLETS ARE HEAVY FOR CALIBER, CONSISTENCE ON TARGET IS DRIVING FACTOR FOR ME. THE MORE CONSISTANCE OF MY LOADS, THE MORE FORGIVING FOR ME AND MY PERFORMANCE. I FOUND PRIMER BRANDS OTHER THAN FEDERAL AND CCI WERE ALL ABOUT SAME IN FPS WITH OUT CHANGING ANY THING ELSE IN LOAD. FEDERAL AND CCI GAVE 100 FPS INCREASE. I USE MAG L RIFLE PRIMERS IN ALL LOADS. ALL THIS OVER TIME I HAVE FOUND TO GIVE GOOD CONSISTANCY FOR WHAT I WANT, AT LONGER RANGES, MOST WILL WORK GREAT AT SHORTER RANGES, I HAVE ONE LOAD FOR MY .223 RIFLE THAT WILL PUT 49/50 IN THE SIZE OF 1" AT 205 YDS, MOVE BACK TO 200 AND I MIGHT AS WELL HAND THROW THEM AT THE TARGET, HAVEN'T FIGERED THIS ONE OUT YET>
    Last edited by BLAHUT; 06-27-2022 at 05:00 PM. Reason: CLARFY,

  15. #55
    Boolit Master
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    The larger the sample group ( shots fired ) the more or better the results, learned.

  16. #56
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    I got a chrony for checking consistency and checking my handloads for "velocity expansion threshold" and fun. I started trying some of the new SD JHP bullets and not wanting to get into the cost and effort of gel, I researched the needed velocities for various bullet performance and matched the velocities in my handloads. I got by quite well for over 30 years without one though...
    My Anchor is holding fast!

  17. #57
    Boolit Grand Master
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    Quote Originally Posted by Larry Gibson View Post
    ...
    Incremental load test is what should be used to develop loads for rifles and handguns. It is the tried and true method developed well before my time. It is the method recommended in most every loading manual ["start low and work up, etc.]. Incremental load testing to develop a load was used for many, many years without the use of a chronograph. Loads were developed using "pressure signs" and groups size. With the advent of the readily usable chronograph with sky screens in the early '70s by Oehler affordable chronographs became a useful tool to further knowledge of what the load was actually doing. Through proper use of the chronograph during incremental load development the best load for a use can be much quicker with less expenditure of time and components. It also can give a much higher confidence level that the load is a good one.
    I have been through this thread a number of times and what Larry posted above is the essence of load development IMO. It is what I have done for five decades and it has worked for me.

    I am not a "long range" shooter but I understand the significance of ES/SD in developing a load for that application. It is easy to work the numbers and understand the effect.

    I have not seen a rationale for focusing on ES/SD for the parameters in my opening post. If a load is accurate enough at 100 yards or 200 yards, it is likely going to be good enough at 300 yards for the .223 and 400 yards for the .308.

    There were two posters on the thread who made me think. One was Wilderness (who does not want the chronograph) and the other was Larry Gibson. I will reach out to them via PM as winners of the challenge.
    Don Verna


  18. #58
    Boolit Master

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    I didn't read all the replies, but plan to when I have a few more minutes.

    Here is why I find a chronograph useful

    1) sanity check on velocity (and therefore relative proxy for pressure) when loading components for which load data is rare or non-existent.

    2) dialing in a specific power factor for shooting games

    3) finding rifle loads with lower extreme spreads
    "There is nothing like looking, if you want to find something."
    ~Thorin Oakenshield

  19. #59
    Boolit Buddy
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    Don – thanks for the wrap.

    Larry – your observations on SD and ES have prompted me to look at some of my old .30-30 cast bullet data. The variables being tested in a 4x2 design were presence or absence of a small amount of PSB filler, against small differences in bullet weight/alloy, and lubes. My conclusion was that none of it made much difference, and that I could therefore regard the whole test as a single series.

    The interesting part for the present discussion is that although the groups for which I had all five velocities showed SD/ES of 35% to 48%, the same data treated as a single series of 37 shots produced an SD of 18 and ES 64, or 28% for SD/ES, which is getting closer to the expected 25%.

    It would appear that these high SD/ES ratios at the 5 and 10 shot level may be quite compatible with a lower SD/ES ratio (25%) at the population level.

    I was going to include the data but cannot figure out how to get a table from Word to CB post.
    Last edited by Wilderness; 07-03-2022 at 07:03 PM.
    It'll be handy if I never need it.

    Insomniac, agnostic, dyslectic - awake all night wondering if there is a Dog.

  20. #60
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    Back in the glory days of endless surplus and pulldown powder, they were nice. You could see big velocity differences from lot to lot.
    In my experience, commercial canister powders are a lot more consistent from lot to lot.
    The surplus powders that are available, no longer carry the bargain basement prices they used to.

    Shiloh
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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check